7046 ‎(3)‎

• UCREFRP Catalog Number: 7046
• Author: Valdez, R. A., W. J. Masslich and A. Wasowicz.
• Title: Final Report\
• USFW Year: 1992.
• Copyright Material: NO

6

I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I

Substrate size was 7 to 25-cm rounded cobble, except for the sample site immediately above the San
Miguel River, which consisted of 15 to 30-cm angular cobble. Two to four sample replicates were
collected within similar habitats at each sample site. Additional qualitative samples were collected
in a range of habitats. Macroinvertebrate samples were preserved in 70% ethanol and transported
to BIO/WEST laboratories for analysis. A Biotic Condition Index (BCI) was calculated for both the
Dolores and San Miguel rivers based on macroinvertebrate collections in 1991, as outlined in the
Fisheries Habitat Surveys Handbook (USFWS 1985).

3.5 Bioassays

Three species of fish were collected for bioassays to assess bioaccumulation of seven heavy metals.
Liver and kidney tissues were collected from flannelmouth suckers, roundtail chub, and channel
catfish in October 1991. Liver and kidney tissue are generally considered good indicators of heavy
metals accumulation (Kunkle et al. 1983, Dallinger and Kautzky 1985, Bradley and Morris 1986).
Attempts were made to collect ten individuals of each species, however only two round tail chub and
six channel catfish could be obtained, Ten flannelmouth suckers were collected for bioassays,
Information collected for each fish included total length, weight, sex and capture location. Liver and
kidney tissues were collected and combined into one sample for each fish. Tissue samples were
immediately frozen in liquid nitrogen and transported to ChemTech Laboratories in Murray, Utah
for analysis,

4.0 RESULTS

4.1 Summary of Fish Collections

A total of 19 species of fisn representing seven families were captured in the Dolores River
during the study (Table 4). This list was similar to that reported by Holden and Stalnaker (1975) and
Valdez et ai, (1982) except that black bullhead, bluegill, plains killifish, brown trout, rainbow trout,
mottled sculpin, white sucker and Colorado squawfish were not reported in 1975 and bluegill, mottled
sculpin and Colorado squawfish were not reported in 1982. White sucker, rainbow trout and brown
trout were reported by Valdez et al. (1982) but were not captured by BIO/WEST in 1990. However,
all three of these species were captured in 1991.

As a percentage of total catch, the most common species of fish captured during the study were
red shiner (33.4), sand shiner (23.1) and fathead minnow (18.4) (Table 5). These three non-native
fish comprised 74.9% of the catch, Of the 19 species reported, 13 were non-native and six were
native or endemic to the Colorado River system (Tyus et al. 1982). Native species comprised 19%
of the total catch and included flannelmouth sucker (9.2), roundtail chub (4.6), bluehead sucker (2.7),
speckled dace (2.5), mottled sculpin ( <0.1) and Colorado squawfish ( <0.1). Four Colorado squawfish
were captured during 1991 in the lower 2 Ian of the Dolores River, These represent the first
Colorado squawfish reported in the drainage since unconfirmed reports by Horpestad in 1973 and
may be the first record since Coon (1965). No other endangered species including bonytail (Gila
elegans), humpback chub (Gila cypha) or razorback sucker (Xyrauchen texanus) were captured in the
Dolores River during the study.

Larval and young-of-year (YOY) life stages of 12 species were captured in the Dolores River
during this study (Table 6.) Four of these 12 species are native or endemic including flannelmouth
sucker, bluehead sucker, roundtail chub and speckled dace, The capture of YOY of these species
during both years of the study indicates that the Dolores River provides adequate habitat for